Improve directory structure

[armcknight]

• [ ] Explode the app/ directory into the parent directory
  • It's annoying to have some config files in root (circle, gemfile, dangerfile, codecov) and some in the app directory (podfile, fastlane, swiftlint). Especially because you have to cd to the app directory to work with cocoapods!
  • Counterpoint: this setup is helpful when there are also going to be server or other non-app components alongside the app in the same repo.
    • Counter-counterpoint: what if we added an android app? then we'd have "app" and what... "android app"? Put android underneath app? Neither of those is good... in this case we should rename "app" to something like "app-ios".
• [ ] Put the entire repo's current contents into a source directory, so we can hold other assets/documentation/automation/etc in this same repo, alongside the project template source. As it is, I see no guides on how to use this, or tools to help–everything appears to be only templating.